2025-01-07 12:19:42 <pgimeno     > well, this is frustrating... as some of you know, I spent several days working on an interpreter for the Jupiter ACE flavour of Forth. That interpreter is now feature-complete, save for SAVE (sorry for the pun) which I will complete next. But...
2025-01-07 12:21:31 <pgimeno     > I need to validate the results, and typing on a real or emulated Juppy is cumbersome, and checking the results is prone to mistakes. So it occurred to me to write a JA emulator that traps the ROM line input and display output routines, and redirects them to a file.
2025-01-07 12:21:49 <xentrac     > congratulations!  that sounds sensible
2025-01-07 12:22:50 <pgimeno     > Now that emulator is written. It cost me about an hour to write. But... it does basically all that my interpreter does, just with 100% guaranteed accuracy. So it makes me wonder, why did I bother to write the interpreter in the first place? *facepalm*
2025-01-07 12:25:03 <pgimeno     > thanks xentrac
2025-01-07 12:28:54 <veltas      > Learning exercise I guess
2025-01-07 12:29:01 <veltas      > Or fun
2025-01-07 12:29:06 <pgimeno     > incidentally, I was quite surprised that the Z80 emulation core I'm using (jgz80) runs at about 8,5 real CPU cycles per Z80 cycle. So in my 3600 MHz machine it's a Z80 running at 425 MHz.
2025-01-07 12:29:12 <veltas      > Both sound cool to me either way
2025-01-07 12:29:51 <veltas      > My favourite Z80 emulator is what fuse (emulator) uses
2025-01-07 12:30:41 <pgimeno     > veltas: Yes, it was both, I give you that :) I got a much better understanding of indirect threading, for one. It also has two advantages, 1) it does not need to be compiled for every target machine, it just needs a Python interpreter; and 2) it does not need the ROM so no copyright issues
2025-01-07 12:30:45 <veltas      > I think 425MHz is a normal speed for interpreting machine code, so I'm assuming it interprets it rather than doing any JIT magic
2025-01-07 12:31:04 <pgimeno     > yeah, totally interpreted
2025-01-07 12:31:34 <veltas      > CPU's are so good that you still get >400MHz easily, which is really cool
2025-01-07 12:32:03 <veltas      > 400MHz Z80 to take over the world lol
2025-01-07 12:34:04 <pgimeno     > I chose this core because it was announced to be fast, and because it turned out to be very simple - monolithic (only 1 header and 1 C file), written in C instead of C++, and just needs 4 callbacks (memory R/W and I/O) to get started. What are the advantages of fuse's core?
2025-01-07 12:35:15 <veltas      > fuse is very mature and runs damn well on even old hardware, all the new speccy emulators don't fit this bill
2025-01-07 12:35:39 <veltas      > But for sake of just the CPU emulation I wouldn't move away from jgz80, if it works
2025-01-07 12:36:07 <pgimeno     > my only "problem" with the jgz80 is that it's too accurate for this purpose (WZ, Q and whatnot), and I could well trade accuracy for speed
2025-01-07 12:36:29 <veltas      > If you want that tradeoff you probably need to write your own
2025-01-07 12:36:39 <veltas      > Everyone emulating Z80 is primarily interested in realism
2025-01-07 12:37:57 <pgimeno     > yeah, you're right, there may be some exceptions (thinking simh for example) but those probably don't care much about speed either
2025-01-07 12:38:45 <pgimeno     > I think rather than writing my own, I could modify jgz80 to remove the extra bloat
2025-01-07 12:39:25 <veltas      > Theoretically 400MHz is already quite good
2025-01-07 12:39:58 <xentrac     > pgimeno: the interpreter is probably more comprehensible, and you can do things like add single-step debugging and stuff
2025-01-07 12:40:02 <pgimeno     > yeah it's about 125 times faster than a juppy
2025-01-07 12:40:02 <veltas      > IMO if you want faster execution, the obvious route is to port the dialect to AMD64 or whatever your CPU is
2025-01-07 12:40:16 <xentrac     > veltas: heh, a 425MHz Z80 sounds great
2025-01-07 12:41:28 <GeDaMo      > http://www.chrisfenton.com/the-zedripper-part-1/ "the ZedRipper – a 16-core, 83 MHz Z80"
2025-01-07 12:41:30 <pgimeno     > for the purpose I'm targeting, I'm happy with how it runs, I'm just a bit too perfectionist when it comes to unnecessary bloat, but if I can get over that, it's pretty fine as is
2025-01-07 12:41:45 <xentrac     > pgimeno: does your interpreter work in PyPy? that might make it a lot faster
2025-01-07 12:41:46 <pgimeno     > oh that sounds cool GeDaMo
2025-01-07 12:42:01 <GeDaMo      > Built in an FPGA
2025-01-07 12:42:09 <veltas      > I got a kick out of rewriting the konilo VM in AMD64
2025-01-07 12:42:38 <pgimeno     > xentrac: sorry, there may be a confusion. My interpreter will probably work in PyPy, but we're talking about the Z80-based Jupiter emulator that I wrote for validating the interpreter.
2025-01-07 12:43:36 <xentrac     > right, I understand
2025-01-07 12:44:18 <pgimeno     > the goal of my interpreter was to enable Jupiter users with the ability to write programs in a PC with modern editors and stuff, and compile them to a tape file for use in emulators or in the real Jupiter. For that purpose, actually not much speed is necessary.
2025-01-07 12:44:56 <xentrac     > more speed always opens up new uses for software
2025-01-07 12:59:05 <veltas      > Lots of stuff opens up new uses, but we don't have infinite time for development!
2025-01-07 13:00:21 <xentrac     > nope, which is why PyPy is so nice :)